//! Run the Mesh OpenAI-compatible reference server — a real
//! `/v1/chat/completions` endpoint any OpenAI client (curl, the SDKs, vLLM-style
//! tooling) can drive, returning energy-metered serving + a sealed receipt.
//!
//! ```text
//! cargo run --example serve --features server -- 127.0.0.1:8088 &
//! curl -s localhost:8088/v1/chat/completions \
//!   -d '{"model":"gpt-mini","messages":[{"role":"user","content":"hi"}],"max_tokens":8}'
//! ```
//!
//! **What a receipt's figure is.** Each request's `usage.energy` carries the
//! energy of the served span — the deterministic reference engine's work, in
//! this process (the HTTP handling around it is outside the span) — at the
//! grade of whatever read it, in `usage.energy.provenance` and in the sealed
//! `mesh/1` receipt. The meter is the one this build can read:
//!
//! - `--features server,metal` (macOS): `mesh_meter::ProcessMeter`, this
//!   process's own CPU and GPU energy over the span. The engine runs in this
//!   process and uses no GPU, so where the GPU counter is proved live its GPU
//!   energy is exactly zero and the span covers the whole request: `HwShunt`,
//!   the kernel's count of this process's CPU energy. That count is every
//!   thread of this process, so a request served while another of its
//!   threads works reads that work too. Where the GPU counter is not proved
//!   live (a GPU busy with other work fails its probe) the span covers part
//!   of the request and is sealed as an estimate of all of it, `Estimator`.
//!   A serve too short for the CPU count to advance over it (this engine's
//!   are microseconds) has no reading either, and is the estimator's figure
//!   for the serve, `Estimator`.
//! - `--features server,hw-meter` (or `hw-meter-rapl`, `-nvml`, `-apple`):
//!   `mesh_meter::HwMeter::detect`, the machine's counter, a reading only
//!   where a live one covers the whole request (a RAPL package on Linux) and
//!   `mesh_meter::EstimatorMeter` otherwise. With `-apple` on a Mac whose
//!   IOReport CPU rail is frozen it is the SMC's whole-machine power: a modeled
//!   figure (`ModelBased`) for a serve at least its 2 s floor long, an estimate
//!   for a shorter one, as this engine's are. A machine counter reads
//!   everything the host does over the span, not this request alone.
//! - `--features server` alone: `mesh_meter::EstimatorMeter`, wall time × an
//!   assumed draw, `Estimator`.
//!
//! No build seals a figure nothing read: a `mesh/1` receipt has no coverage
//! field, so `HwShunt` there claims a hardware reading of the whole request
//! (SPEC §3.3), and only a meter that read one may say so.

use std::net::TcpListener;

use ed25519_dalek::SigningKey;
use mesh_core::Mesh;
use mesh_engine::ReferenceEngine;
use mesh_meter::Meter;
use mesh_openai::{server, ChatBackend};
use mesh_router::BackendSpec;
use mesh_schema::Fidelity;

/// A trivial tokenizer bridge: bytes in, a deterministic note out. A real
/// deployment pairs the model's own tokenizer with the engine that serves it.
pub struct ByteBackend;
impl ChatBackend for ByteBackend {
    fn encode(&self, text: &str) -> Vec<u32> {
        text.bytes().map(u32::from).collect()
    }
    fn decode(&self, ids: &[u32]) -> String {
        format!("[mesh reference engine served {} tokens]", ids.len())
    }
}

/// The meter this build serves with: see the module docs for each feature's
/// meter and what its figures cover.
pub fn meter() -> Box<dyn Meter> {
    #[cfg(feature = "metal")]
    let meter: Box<dyn Meter> = Box::new(mesh_meter::ProcessMeter::new(
        jouleclaw_backend_apple::gpu_liveness_load,
        mesh_meter::SpanUses::CpuGpu,
    ));
    #[cfg(all(feature = "hw-meter", not(feature = "metal")))]
    let meter: Box<dyn Meter> = Box::new(mesh_meter::HwMeter::detect());
    #[cfg(not(feature = "hw-meter"))]
    let meter: Box<dyn Meter> = Box::new(mesh_meter::EstimatorMeter::default());
    meter
}

/// The deterministic reference engine behind one steward-signed receipt
/// chain, metered by `meter`.
pub fn mesh(meter: &dyn Meter) -> Mesh<'_> {
    let sk = SigningKey::from_bytes(&[8u8; 32]);
    let mut mesh = Mesh::new(meter, sk, "did:example:mesh-demo");
    mesh.register(
        BackendSpec::new("tiny", "ssm-1b", Fidelity::F2, 50_000),
        Box::new(ReferenceEngine::new("tiny", "ssm-1b", Fidelity::F2, 50_000, 32)),
    );
    mesh
}

fn main() -> std::io::Result<()> {
    let addr = std::env::args().nth(1).unwrap_or_else(|| "127.0.0.1:8088".to_string());
    let listener = TcpListener::bind(&addr)?;
    let meter = meter();
    eprintln!("mesh OpenAI server: http://{addr}/v1/chat/completions (meter: {})", meter.name());
    let mut mesh = journalled(mesh(meter.as_ref()))?;
    server::run(&listener, &mut mesh, &ByteBackend, 100_000_000)
}

/// With `MESH_JOURNAL` set, record grant decisions and seals in that file and
/// replay what it already holds before serving, so a restart gives no budget
/// back and the receipt chain continues (Mesh SPEC §2.2). Without it the
/// journal is in memory, which a steward that restarts must not rely on.
pub fn journalled(mesh: mesh_core::Mesh<'_>) -> std::io::Result<mesh_core::Mesh<'_>> {
    let Some(path) = std::env::var_os("MESH_JOURNAL") else {
        return Ok(mesh);
    };
    let (journal, recorded) = mesh_core::FileJournal::open(&path)?;
    let mesh = mesh
        .with_journal(journal, &recorded)
        .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e.to_string()))?;
    for u in mesh.unresolved() {
        eprintln!("unresolved: request {} on backend {}, debited {} µJ", u.request_id.to_hex(), u.backend, u.debited_uj);
    }
    Ok(mesh)
}